1. Field of the Invention
The present invention relates generally to a socalled picture-in-picture type television receiver in which a sub-picture screen is inset into a main picture screen in a picture-in-picture fashion.
2. Description of the Prior Art
There is known a so-called picture-in-picture type television receiver in which a sub-picture screen is provided within a main picture screen such that pictures having different contents can be displayed on the main and sub-picture screens, respectively. According to this prior art television receiver, the television channels of the main picture and the sub-picture or the number of an external video signal input terminal are displayed on a front panel of the television receiver using a display apparatus such as an LED (light emitting diode) and the like or these numbers are displayed on the picture screen of the cathode ray tube. When these numbers, which are referred to herein as discrimination indications, are displayed on the screen, they are displayed on the main picture screen together.
Further, the picture-in-picture type television receiver is provided with a main tuner for selecting the video signal for the main picture screen and a sub-tuner for selecting a video signal for the sub-picture screen. In such a prior art television receiver, it is preferable that the channel selection operations can be carried out independently in the main and sub-tuners. Thus, the discrimination indications of the picture contents, for example, the indications of the channels selected, are independently carried out on the main and sub-picture screens in response to the respective channel selection operations.
However, in the prior art picture-in-picture type television receiver, the picture discrimination indications for discriminating the main picture screen and the sub-picture screen can not be positively carried out. There is no problem when the selected channel of the sub-tuner is changed, in that the change in the discrimination indication of the picture content is carried out only on the sub-picture screen. However, when the selected channel of the main tuner is changed, it causes a problem in that the picture discrimination indication for the picture content is carried out only on the main picture screen. That is, since it is apt to be regarded that the picture displayed on the sub-picture screen is subjected to the picture displayed on the main picture screen, in this case, it is preferable that the discrimination indication for the picture content is carried out also on the sub-picture screen.